/*
 * Copyright 2008-present MongoDB, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mongodb.selector;

import com.mongodb.connection.ClusterDescription;
import com.mongodb.connection.ServerDescription;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

import static com.mongodb.assertions.Assertions.notNull;

A server selector that composes a list of server selectors, and selects the servers by iterating through the list from start to
finish, passing the result of the previous into the next, and finally returning the result of the last one.
Since:
3.0/**
 * A server selector that composes a list of server selectors, and selects the servers by iterating through the list from start to
 * finish, passing the result of the previous into the next, and finally returning the result of the last one.
 *
 * @since 3.0
 */
public final class CompositeServerSelector implements ServerSelector {
    private final List<ServerSelector> serverSelectors;

    
Constructs a new instance.
Params:
serverSelectors – the list of composed server selectors/**
     * Constructs a new instance.
     *
     * @param serverSelectors the list of composed server selectors
     */
    public CompositeServerSelector(final List<? extends ServerSelector> serverSelectors) {
        notNull("serverSelectors", serverSelectors);
        if (serverSelectors.isEmpty()) {
            throw new IllegalArgumentException("Server selectors can not be an empty list");
        }
        ArrayList<ServerSelector> mergedServerSelectors = new ArrayList<ServerSelector>();
        for (ServerSelector cur : serverSelectors) {
            if (cur == null) {
                throw new IllegalArgumentException("Can not have a null server selector in the list of composed selectors");
            }
            if (cur instanceof CompositeServerSelector) {
                mergedServerSelectors.addAll(((CompositeServerSelector) cur).serverSelectors);
            } else {
                mergedServerSelectors.add(cur);
            }
        }
        this.serverSelectors = Collections.unmodifiableList(mergedServerSelectors);
    }

    
Returns:
the server selectors list./**
     * @return the server selectors list.
     */
    public List<ServerSelector> getServerSelectors() {
        return serverSelectors;
    }

    @Override
    public List<ServerDescription> select(final ClusterDescription clusterDescription) {
        ClusterDescription curClusterDescription = clusterDescription;
        List<ServerDescription> choices = null;
        for (ServerSelector cur : serverSelectors) {
            choices = cur.select(curClusterDescription);
            curClusterDescription = new ClusterDescription(clusterDescription.getConnectionMode(), clusterDescription.getType(), choices,
                                                                  clusterDescription.getClusterSettings(),
                                                                  clusterDescription.getServerSettings());
        }

        return choices;
    }

    @Override
    public boolean equals(final Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        CompositeServerSelector that = (CompositeServerSelector) o;
        if (serverSelectors.size() != that.serverSelectors.size()) {
            return false;
        }
        return serverSelectors.equals(that.serverSelectors);
    }

    @Override
    public int hashCode() {
        return serverSelectors != null ? serverSelectors.hashCode() : 0;
    }

    @Override
    public String toString() {
        return "{"
               + "serverSelectors=" + serverSelectors
               + '}';
    }
}